Recombinant DNA technology has made it possible to insert foreign DNA sequences into the genome of an organism, thus, altering the organism's phenotype. The most commonly used plant transformation methods are Agrobacterium infection and biolistic particle bombardment in which transgenes integrate into a plant genome in a random fashion and with an unpredictable copy number.
Site-specific integration techniques, which employ site-specific recombination systems, as well as, other types of recombination technologies, have been used to generate targeted insertions of genes of interest in a variety of organism.
Other methods for inserting or modifying a DNA sequence involve homologous DNA recombination by introducing a transgenic DNA sequence flanked by sequences homologous to the genomic target. U.S. Pat. No. 5,527,695 describes transforming eukaryotic cells with DNA sequences that are targeted to a predetermined sequence of the eukaryote's DNA. Transformed cells are identified through use of a selectable marker included as a part of the introduced DNA sequences.
While both systems have provided useful techniques for targeted insertion of sequences of interest, there remains a need for methods and compositions which improve these systems and allow for a gene of interest to be targeted to a specific site in the plant genome.